EP1626442B1 - Capteur d'image - Google Patents

Capteur d'image Download PDF

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Publication number
EP1626442B1
EP1626442B1 EP05107383A EP05107383A EP1626442B1 EP 1626442 B1 EP1626442 B1 EP 1626442B1 EP 05107383 A EP05107383 A EP 05107383A EP 05107383 A EP05107383 A EP 05107383A EP 1626442 B1 EP1626442 B1 EP 1626442B1
Authority
EP
European Patent Office
Prior art keywords
microlens
photosensitive
image sensor
photosensitive area
forming
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP05107383A
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German (de)
English (en)
French (fr)
Other versions
EP1626442A3 (fr
EP1626442A2 (fr
Inventor
Jérôme VAILLANT
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STMicroelectronics SA
Original Assignee
STMicroelectronics SA
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Filing date
Publication date
Application filed by STMicroelectronics SA filed Critical STMicroelectronics SA
Publication of EP1626442A2 publication Critical patent/EP1626442A2/fr
Publication of EP1626442A3 publication Critical patent/EP1626442A3/fr
Application granted granted Critical
Publication of EP1626442B1 publication Critical patent/EP1626442B1/fr
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14625—Optical elements or arrangements associated with the device
    • H01L27/14627—Microlenses

Definitions

  • the present invention relates to an image sensor comprising a matrix of photosensitive cells arranged in rows and columns and made in a CMOS technology.
  • the figure 1 schematically represents an image sensor consisting of a matrix of pixels 1 receiving by an objective 2, the image of a distant object plane 3.
  • the image of a point A situated in the middle of the object plane will form substantially in the middle of the matrix 1.
  • the image of a point B located at the edge of the object plane will form at the edge of the matrix 3.
  • the figure 2 is a sectional view of a substantially central photosensitive cell 6 of an image sensor formed on a substrate 7, for example silicon.
  • the photosensitive cell 6 is associated with a portion of the surface of the substrate 7 which, seen from above, generally has the shape of a square or a rectangle.
  • the photosensitive cell 6 comprises a photosensitive active zone 8 generally corresponding to a photodiode adapted to store a quantity of electric charges as a function of the light intensity received.
  • the substrate 7 is covered with a stack of transparent insulation layers 9, 11, 12, 13 which may be, for example, alternately silicon oxide and silicon nitride.
  • the conductive tracks 14 and conductive vias 16 are generally metallic. Examples include aluminum, tungsten, copper and metal alloys. These materials are opaque and possibly reflective.
  • a color filter element 17 for example an organic filter, is arranged on the stack of the insulation layers 9, 11, 12, 13 at the level of the photosensitive cell 6.
  • the filter elements of color 17 are generally covered with a planarized equalizing layer 18 which defines an exposure face 19 exposed to light.
  • a microlens 21 is disposed on the equalization layer 18, facing each other of the photosensitive zone 8 to focus the light rays towards the photosensitive zone 8.
  • the paths of two light rays R1, R2 are schematically represented by way of example for the photosensitive cell 6.
  • the conductive tracks 14 and the conductive vias 16 are arranged so as not to hinder the passage of light rays.
  • the microlens 21 is for example obtained by covering the equalization layer 18 with a resin. The resin is etched to delimit distinct resin blocks, each resin block being formed substantially vis-à-vis a photosensitive area 8. The resin blocks are then heated.
  • the photosensitive zone 8 covers only a portion of the surface of the substrate 7 associated with the photosensitive cell 6. Indeed, part of the surface is reserved for addressing and reading devices of the photosensitive zone 8. of clarity, these devices have not been shown on the figure 2 .
  • the figure 3 is a sectional view of a photosensitive cell 6 of an image sensor located at the edge of the pixel array.
  • two radii R1 ', R2' are represented. It is observed that the focusing of the rays R 1 'and R 2' is next to the photosensitive zone 8. Thus, at least a part of the light spot provided by the microlens 21 does not fall on the photosensitive zone 8 and the edges of the photosensitive zone 8. image, for the same illumination, appear darker than the center of the image. This results in a loss of peripheral sensitivity due to the shift of the projected image on the peripheral parts of the matrix of photosensitive cells.
  • the distance T between the microlens 21 and the photosensitive zone 8 does not generally vary significantly.
  • the ratio between the distance T and the lateral dimension d therefore tends to increase.
  • the microlens 21 must therefore be less convergent to allow focusing on the photosensitive zone 8.
  • the microlens 21 must be thinner, which implies that the resin layer deposited on the equalization layer 18 must be thinner.
  • a third limitation of the current manufacturing process results from the presence of conductive tracks 14 and conductive vias 16 which can be obstacles and impede the passage of light rays.
  • the document US 2003/0168679 discloses an image sensor comprising two microlenses that converge together light at the photosensitive area.
  • the document JP11040787 discloses an image sensor comprising microlenses that also allow improved overflow.
  • the object of the present invention is to propose an image sensor constituted by a matrix of photosensitive cells making it possible to focus, for each photosensitive cell, more light on the photosensitive zone of the photosensitive cell than the image sensor described in state of the art.
  • Another object of the present invention is to overcome the loss of peripheral sensitivity of an image sensor.
  • the present invention provides an image sensor pixel structure comprising a photosensitive area, a stack of isolation layers covering the photosensitive area, and a light focusing device of the pixel to the photosensitive area.
  • the focusing device comprises first and second microlenses, the first microlens being disposed between layers of the stack and conjugating the second microlens with the photosensitive area.
  • the senor comprises a light exposure face and the second microlens is located on the exposure face.
  • the first microlens is made of a first material having a first refractive index
  • the layers of the stack adjacent to the first microlens being made of a second material having a second index of refraction less than the first refractive index
  • the first microlens is based on silicon nitride between two layers of silicon oxide.
  • the first microlens is disposed substantially at one third of the distance between the second microlens and the photosensitive zone.
  • the invention also relates to an image sensor comprising a set of pixel structures such as above.
  • the optical axis of the first microlens and the optical axis of the second microlens of at least one pixel structure of the entire pixel structure are parallel and offset.
  • the shift between the optical axis of the first microlens and the optical axis of the second microlens is increased as one moves away from the center of the image sensor.
  • the invention also provides a method of manufacturing an image sensor, comprising the steps of forming a photosensitive area at a substrate; forming a first stack of isolation layers; forming for the photosensitive zone a first microlens; forming a second stack of isolation layers; and forming for the photosensitive area a second microlens such that for the photosensitive area, the corresponding first microlens conjugates the corresponding second microlens with said photosensitive area.
  • the step of forming the first microlens comprises the following steps: depositing a layer based on silicon nitride; deposit a layer of resin on the first stack; forming, vertically above each desired position of a first microlens, a resin block having the desired shape of the first microlens; and etch the resin block and the silicon nitride layer to form the first microlens in the silicon nitride layer, the first microlens having the shape of the associated resin block.
  • the figure 4 is a sectional view of an exemplary embodiment of a photosensitive cell 26 of an image sensor.
  • the cell 26 has substantially the same structure as the cell 6 of the figure 2 .
  • the cell photosensitive material 26 comprises a microlens 29.
  • a planarized equalization layer 18 covers the filter element 17, the upper face of the layer 18 constitutes the exposure face 19 exposed to the light on which a microlens 27 is arranged.
  • the focal length microlens 29 is chosen so that the microlens 29 forms the image of the microlens 27 on the associated photosensitive zone 8.
  • the microlens 29 conjugates the plane of the microlens 27 and that of the associated photosensitive zone 8, with a magnification less than or equal to the ratio between the size d of the photosensitive zone and the size of the photosensitive cell 26 ( or microlens 27).
  • a focusing device has been formed for focusing the light towards the photosensitive zone 8.
  • the optical axis of the microlens 29 is substantially coincident with that of the microlens 27.
  • the exemplary R3 and R4 rays converge on the microlens 29. the microlens 29, unlike the rays R1 and R2, which themselves converged directly on the photosensitive zone 8.
  • the microlens 27 is therefore more convergent than the microlens 21.
  • the outer surface 28 of the microlens 27 is more curved and therefore easier to develop by the standard creep manufacturing process.
  • a first advantage of the present invention therefore lies in the implementation of a simpler, more reliable and therefore more repeatable microlensing method 27.
  • the figure 5 is a sectional view of a photosensitive cell 26 located at the pixel matrix edge.
  • Light rays R3 'and R4' have been shown by way of example.
  • the microlens 29 conjugating the microlens 27 with the photosensitive zone 8, the rays R3 'and R4' converge on the microlens 29.
  • the image is then reconstituted on the photosensitive zone 8 without loss of luminous intensity or resolution although the structure pixel is at the edge of the matrix.
  • a second advantage of the present invention is therefore an improvement in the peripheral sensitivity during the restitution of the image on the photosensitive zone 8 resulting from an automatic refocusing of the image of a peripheral zone.
  • FIGS. 6A, 6B and 6C represent a photosensitive cell according to the invention at different stages of an exemplary method of manufacturing an image sensor according to the invention.
  • the Figure 6A illustrates the result of first steps of manufacturing a pixel structure.
  • the photosensitive zones 8 are formed by ion implantation of P type dopants.
  • An isolation layer 9 is then deposited in which conductive vias 16 are formed.
  • conductive tracks 14 are produced before depositing a second insulating layer 11.
  • the same procedure as above is followed for the production of conductive vias 16 and conductive tracks 14 associated with isolation layer 11 before re-depositing an insulation layer 12.
  • the insulation layer 12 is for example made of silicon nitride whereas the insulation layer 11 is for example made of silicon oxide.
  • a layer of resin 32 is then deposited.
  • the Figure 6B illustrates a curved structure 33 obtained after etching the resin layer 32 and creeping the etched resin blocks.
  • the next step is a step of uniform etching in the direction of the arrows 34.
  • the curved resin structure 33 and the insulation layer 12 are etched uniform and selective with respect to the insulation layer 9 and the conductive tracks 14 by plasma etching.
  • the shape of the curved structure 33 is reproduced at the level of the layer 11. Such a step is called shape transfer.
  • the Figure 6C represents the structure obtained at the end of the shape transfer step which results in the shape of the microlens 29.
  • the present invention is susceptible of various variations and modifications which will be apparent to those skilled in the art.
  • the devices presented in the exemplary embodiments have been for devices comprising two levels of conductive tracks 14 and two levels of conductive vias 16. These devices can be made with a number of levels of conducting tracks 14 and levels. of conductive vias 16 lower or higher.
  • the position of the microlens 29 may vary and therefore not necessarily be above the second level of conductive vias 16. In fact the microlens 29 may be performed in a lower or higher level.
  • the microlens 29 may be based on silicon nitride and be in a SiNO type compound.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electromagnetism (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
  • Solid State Image Pick-Up Elements (AREA)
  • Light Receiving Elements (AREA)
EP05107383A 2004-08-13 2005-08-11 Capteur d'image Active EP1626442B1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR0451847 2004-08-13

Publications (3)

Publication Number Publication Date
EP1626442A2 EP1626442A2 (fr) 2006-02-15
EP1626442A3 EP1626442A3 (fr) 2007-02-28
EP1626442B1 true EP1626442B1 (fr) 2011-01-12

Family

ID=34947097

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05107383A Active EP1626442B1 (fr) 2004-08-13 2005-08-11 Capteur d'image

Country Status (4)

Country Link
US (1) US7291826B2 (ja)
EP (1) EP1626442B1 (ja)
JP (1) JP2006054469A (ja)
DE (1) DE602005025834D1 (ja)

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7208783B2 (en) * 2004-11-09 2007-04-24 Micron Technology, Inc. Optical enhancement of integrated circuit photodetectors
US20060193356A1 (en) * 2005-01-18 2006-08-31 Robert Osiander Die level optical transduction systems
CN100570877C (zh) * 2005-07-08 2009-12-16 株式会社尼康 固态成像传感器
US7544982B2 (en) * 2006-10-03 2009-06-09 Taiwan Semiconductor Manufacturing Company, Ltd. Image sensor device suitable for use with logic-embedded CIS chips and methods for making the same
US7978255B2 (en) * 2007-10-11 2011-07-12 Nikon Corporation Solid-state image sensor and image-capturing device
JP5157436B2 (ja) * 2007-10-11 2013-03-06 株式会社ニコン 固体撮像素子および撮像装置
KR100896876B1 (ko) * 2007-11-16 2009-05-12 주식회사 동부하이텍 이미지 센서 및 그 제조방법
US8183510B2 (en) * 2008-02-12 2012-05-22 Omnivision Technologies, Inc. Image sensor with buried self aligned focusing element
US7589306B2 (en) * 2008-02-12 2009-09-15 Omnivision Technologies, Inc. Image sensor with buried self aligned focusing element
JP2011100900A (ja) * 2009-11-06 2011-05-19 Sony Corp 固体撮像装置及びその製造方法と設計方法並びに電子機器
US8981510B2 (en) * 2010-06-04 2015-03-17 Taiwan Semiconductor Manufacturing Company, Ltd. Ridge structure for back side illuminated image sensor
TWI649794B (zh) 2012-11-08 2019-02-01 日商半導體能源研究所股份有限公司 金屬氧化物膜及形成金屬氧化物膜的方法
FR3018954B1 (fr) * 2014-03-20 2017-07-21 Commissariat Energie Atomique Procede d'optimisation du rendement quantique d'une photodiode
KR102472276B1 (ko) 2016-03-24 2022-11-29 에스케이하이닉스 주식회사 이미지 센서
CN109411498A (zh) * 2018-10-30 2019-03-01 德淮半导体有限公司 图像传感器及其形成方法

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3044734B2 (ja) * 1990-03-30 2000-05-22 ソニー株式会社 固体撮像素子
US5739548A (en) * 1995-05-02 1998-04-14 Matsushita Electronics Corporation Solid state imaging device having a flattening layer and optical lenses
JP3405620B2 (ja) * 1995-05-22 2003-05-12 松下電器産業株式会社 固体撮像装置
JP3809708B2 (ja) * 1997-07-15 2006-08-16 ソニー株式会社 固体撮像素子並びにその製造方法
JP3620237B2 (ja) * 1997-09-29 2005-02-16 ソニー株式会社 固体撮像素子
JP3571909B2 (ja) * 1998-03-19 2004-09-29 キヤノン株式会社 固体撮像装置及びその製造方法
JP3789365B2 (ja) * 2002-01-31 2006-06-21 シャープ株式会社 層内レンズ付き半導体装置およびその製造方法
JP2003229553A (ja) * 2002-02-05 2003-08-15 Sharp Corp 半導体装置及びその製造方法
US20060151818A1 (en) * 2002-09-27 2006-07-13 Yoshinori Toumiya Solid state imaging device and production method therefor
US7372497B2 (en) * 2004-04-28 2008-05-13 Taiwan Semiconductor Manufacturing Company Effective method to improve sub-micron color filter sensitivity

Also Published As

Publication number Publication date
DE602005025834D1 (de) 2011-02-24
US20060033008A1 (en) 2006-02-16
EP1626442A3 (fr) 2007-02-28
US7291826B2 (en) 2007-11-06
JP2006054469A (ja) 2006-02-23
EP1626442A2 (fr) 2006-02-15

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